What is the purpose of a high voltage disconnect switch?

Disconnect switches establish isolation points to enable equipment maintenance. They are installed on both sides of the circuit breaker, high-side of the transformer, and on the line exit.

Disconnect Switch: Learn the Purpose, Cost, and Lead Time to Procure

Purpose of disconnect switch

Disconnect switches establish isolation points to enable equipment maintenance. They are installed on both sides of the circuit breaker, high-side of the transformer, and on the line exit.

Location of disconnect switches inside a substation

Switches cannot and should not be used to interrupt load current or fault current. A switch operation takes place after the circuit is de-energized.

Cost of disconnect switch

A switch can be designed in numerous ways – vertical break, center break, side break, double side break, pantograph, etc. View some of them here. The prices below reflect your typical vertical break configuration.

365kV 3000A motor operated disconnect switch: ~$50,000
138kV 2000A motor operated disconnect switch: ~$20,000

Lead time to procure disconnect switch

~22 weeks for a high voltage switch.

Information on cost and lead time is for your general knowledge only. Contact vendor with your equipment specifications for actual figures.

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Disconnect Switch: Learn the Purpose, Cost, and Lead Time to Procure 1

Substation Major Equipment

It’s only stupid-simple, let’s begin.

An industrial facility is plagued with voltage flicker and poor power factor at the service entrance. What’s the remedy?

Harmonic filter bank

Voltage regulator

Install capacitor bank

You are building an interconnect station, tying wind farm generation to the power grid. At the substation, the sources are tied through a tie-breaker. Which device would you install to check voltage magnitude and synchronization?

Voltage transformer

Ideal transformer

Current transformer

Power transformer

What’s the purpose of a conventional power transformer?

Transform voltage only

Transform voltage and current

Transform power, voltage, and current

Which combination of devices would you use to implement power line carrier?

Wavetrap, capacitor coupled voltage transformer, and line tuner

Wave trap, capacitor voltage transformer and line tuner

Wave trap and line tuner

A transformer develops an internal fault. Which device would you install on the transformer high-side to interrupt fault current?

Either a breaker or a circuit switcher

Disconnect switch

Circuit switcher

Circuit breaker

For which event should a surge arrester operate? Check all that apply.

Lightning strike

Temporary overvoltage

Phase-to-ground short-circuit

Switching surge

In a distribution substation, the available ground-fault current on the low side of the step-down transformer is excessive, over-dutying the switching equipment. What is your cost-effective solution to reducing the fault current?

Buy new transformer with higher impedance (%Z)

Add current limiting fuses in series on the switchgear

Add inductor in the transformer neutral

Add series inductors

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The average score is 38%